Field of the Invention
The present invention relates to the construction of arched structures and, in particular, to a formwork for use in the construction of arched structures and a method of constructing arched structures.
Description of the Related Art
It is known to use arched structures in bridges, culverts, sewers and tunnels among other things. Traditionally, arched structures were constructed by successively setting voussoirs until a central voussoir or keystone can be set. The arched structure then becomes complete and self-supporting. Compressive forces hold the voussoirs together in a state of equilibrium and, in theory, may provide the arched structure with an indefinite lifespan. Arched structures constructed during the time of the Roman Empire still stand today. There are however significant limitations to traditional methods of constructing arched structures, the foremost being the time consuming processes of setting the voussoirs and moving a formwork forward to lengthen the arched structure.
Following the development of modern hydraulic cement, and the increased use of concrete in construction, arched structures are now typically constructed by casting concrete on arch shaped linings. This allows for the rapid construction of arched structures of varying lengths. However, concrete cast arched structures often require reinforcement bars to resist forces other than compressive forces. This limits the lifespan of concrete cast arched structures as even epoxy coated, galvanized and stainless steel reinforcement bars eventually corrode. Corrosion of the reinforcement bars may lead to the cracking, spalling and ultimately structural failure of the arched structure.
There is accordingly a need for an improved system and method of constructing arched structures.